Lithium rechargeable battery

ABSTRACT

A lithium rechargeable battery includes an insulation case positioned on top of an electrode assembly where the insulation case has least one hole to improve the stability of the battery by evacuating gas that may be generated by the electrode assembly.

This application claims priority to and the benefit of Korean PatentApplication No. 10-2004-0083268, filed on Oct. 18, 2004, which is herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lithium rechargeable battery adaptedto more easily evacuate gas generated inside the battery and improve thestability of the battery.

2. Discussion of the Background

As portable electronic appliances continue to be made lighter and morecompact, small-sized high-capacity batteries have become increasinglynecessary as a power source. Lithium rechargeable batteries areincreasingly used in the industry because they have a high energydensity per unit weight and an operating voltage of 3.6V, which is threetimes larger than that of nickel-hydrogen or nickel-cadmium batteries.

Lithium rechargeable batteries create electric energy by oxidation andreduction reactions that occur during intercalation and deintercalationof lithium ions at the positive and negative electrodes. Materialsenabling lithium ions to undergo reversible intercalation anddeintercalation are used as the active materials of the positive andnegative electrodes. An organic electrolyte or a polymer electrolyte isused to fill the space between the positive and negative electrodes.

Lithium-containing metal oxide may be used as the positive electrodeactive material of the lithium rechargeable batteries. Examples of alithium-containing metal oxide include lithium cobalt oxide (LiCoO₂),lithium nickel oxide (LiNiO₂), and lithium manganese oxide (LiMnO₂).

Lithium or lithium alloy is conventionally used as the negativeelectrode active material. Lithium has the drawback that the batteriestend to short-circuit and explode due to dendrite formation. To overcomethis problem, lithium has been replaced by carbon-based materials,including amorphous and crystalline carbon. The lithium rechargeablebatteries are manufactured in various shapes including cylinders,squares, and pouch types.

FIG. 1 is an exploded perspective view showing a conventional lithiumrechargeable battery.

Referring to FIG. 1, a lithium rechargeable battery is formed by placingan electrode assembly 12 including a first electrode 13, a secondelectrode 15, a separator 14, and an electrolyte into a can 10 andsealing the opening of the can 10 with a cap assembly 70.

The cap assembly 70 includes a cap plate 71, an insulation plate 72, aterminal plate 73, and an electrode terminal 74. The cap assembly 70 iscoupled to the opening of the can 10 and to a separate insulation case79 that seals the can 10.

The cap plate 71 is made of a metal plate with a size and a shapecorresponding to the shape of the opening of the can 10. The cap plate71 has a terminal through-hole of predetermined size formed at itscenter, into which the electrode terminal 74 is inserted. A tubulargasket 75 is coupled to the outer surface of the electrode terminal 74to insulate the electrode terminal 74 from the cap plate 71. The capplate 71 has an electrolyte injection hole 76 of predetermined sizeformed on a side. The cap assembly 70 is connected to the top opening ofthe can 10. An electrolyte is injected via the electrolyte injectionhole 76, and the electrolyte injection hole 76 is then sealed by a plug77.

The electrode terminal 74 is electrically connected to a secondelectrode tab 17 of the second electrode 15 or to a first electrode tab16 of the first electrode 13 via the terminal plate 73, which acts as asecond or first electrode terminal. Insulation tapes 18 are wound aroundportions of the electrode assembly 12 through which the first electrodetab 16 and the second electrode tab 17 are drawn to avoid a shortcircuit between the electrodes 13 and 15. The first electrode 13 or thesecond electrode 15 may act as either a positive electrode or a negativeelectrode.

A conventional lithium rechargeable battery is in danger of fracture ifthe voltage abruptly rises due to an internal or external short circuitor overcharging or over-discharging of the electrode assembly. When thebattery is overcharged, excessive deintercalation of lithium occurs atthe positive electrode and excessive intercalation of lithium occurs atthe negative electrode. This renders the positive and negativeelectrodes thermally unstable and generates radical heating reactions,including decomposition of the organic solvent of the electrolyte,reaction between the negative electrode active material and theelectrolyte, and solid electrolyte interface (SEI) film thermaldecomposition reaction of the negative electrode. In addition, a thermalrunaway phenomenon occurs and seriously degrades the stability of thebattery.

The lithium rechargeable battery is equipped with a safety device, suchas a positive temperature coefficient (PTC) thermistor or a safety ventto prevent the battery from catching fire or exploding due to anabnormality. The safety vent is formed on the cap plate or on the canand is adapted to open at a predetermined pressure to evacuate gasinside the battery to the exterior.

Despite being equipped with such a safety device, the danger remainsthat the safety device may fail to function in time to avoid a fractureif gas is not properly evacuated from the electrode assembly.

SUMMARY OF THE INVENTION

The present invention provides a lithium rechargeable battery thatincludes an insulation case that is provided with a hole to evacuate gasgenerated from an electrode assembly to a safety vent and therebyimprove the stability of the battery.

Additional features of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention.

The present invention discloses a lithium rechargeable battery thatincludes an electrode assembly with first and second electrodes woundtogether with a separator interposed between them, an insulation casepositioned on top of the electrode assembly, and a can containing theelectrode assembly and the insulation case, where the insulation casehas at least one of an electrolyte injection hole and an electrode tabdrawing hole, and at least one other hole.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrated embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 shows an exploded perspective view of a conventional lithiumrechargeable battery.

FIG. 2 a shows a perspective view of an insulation case according to anexemplary embodiment of the present invention.

FIG. 2 b shows a top view of the insulation case shown in FIG. 2 a.

FIG. 3 a shows a perspective view of an insulation case according to anexemplary embodiment of the present invention.

FIG. 3 b shows a top view of the insulation case shown in FIG. 3 a.

FIG. 4 a shows a perspective view of an insulation case according to anexemplary embodiment of the present invention.

FIG. 4 b shows a top view of the insulation case shown in FIG. 4 a.

FIG. 5 a shows a perspective view of an insulation case according to anexemplary embodiment of the present invention.

FIG. 5 b shows a top view of the insulation case shown in FIG. 5 a.

FIG. 6 shows a sectional view of a lithium rechargeable batteryaccording to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

According to an exemplary embodiment of the present invention, a lithiumrechargeable battery includes an insulation case provided with a hole tomore easily evacuate gas that may be generated due to overcharging orshort-circuiting. The evacuation of gas improves the stability of thebattery.

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which embodiments of the invention are shown.This invention may, however, be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure isthorough, and will fully convey the scope of the invention to thoseskilled in the art. In the drawings, the size and relative sizes oflayers and regions may be exaggerated for clarity.

It will be understood that when an element such as a layer, film, regionor substrate is referred to as being “on” another element, it can bedirectly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” another element, there are no intervening elements present.

Referring to FIG. 2 a and FIG. 2 b, an insulation case 179 for a lithiumrechargeable battery according to an exemplary embodiment of the presentinvention includes a main body 181, at least one hole 190 a formed onthe main body 181, short supporters 183 and 184, and long supporters 185and 186. The main body 181 is shaped so that it can be inserted into acan of the lithium rechargeable battery.

The main body 181 has a circular hole 190 a formed on its short side.The hole 190 a acts as an evacuation conduit to move gas that may begenerated when the battery short-circuits or overcharges to a safetyvent so that the gas can escape more easily. The hole 190 a prevents theelectrode assembly from expanding and improves the battery's stabilityby facilitating the actuation of the safety vent when the internalpressure of the battery rises.

The hole 190 a may have any shape, including, but not limited to, acircle, an ellipse, a semi-circle, a square, a triangle, a lozenge, andany combination thereof. The hole 190 a may be formed anywhere on themain body 181 a, including on a long side, a short side, or the centralportion. The structural integrity of the main body 181 is bestmaintained when the hole 190 a is positioned on a side of the main body181, particularly on a short side. The hole 190 a may also be formed asa groove cut out of the edge of the main body 181.

The hole 190 a may be positioned near a safety vent, for example, belowor directly below the safety vent. The hole 190 a most easilyfacilitates the actuation of the safety vent on the can or cap platewhen it is located directly below the safety vent.

The size and number of the holes 190 a are selected so as to avoiddegrading the structural integrity of the main body 181. Otherwise, themain body 181 may deform and cause the battery to short-circuit when thebattery is subjected to a physical impact, for example, during a droptest.

The main body 181 has short side supporters 183 and 184 formed on itsshort side. The short side supporters 183 and 184 extend upward to apredetermined height. The short side supporters 183 and 184 support themain body 181 and enhance the adhesion of the main body 181 to the innerwall of the can to prevent the insulation case 179 from floating whenthe insulation case 179 is placed into the can.

The main body 181 may have at least one long side supporter 185 and 186formed on its long side. The long side supporters 185 and 186 extendupward to a predetermined height. The height of the long side supporters185 and 186 may be identical to the height of the short side supporters183 and 184. The long side supporters 185 and 186 are placed in apredetermined position on the long side of the main body 181. The longside supporters 185 and 186 reinforce the strength of the long side ofthe main body 181, which is weaker than the short side, and prevent themain body 181 from deforming when the battery is subjected to physicalimpact.

The short side supporters 183 and 184 and the long side supporters 185and 186 may be formed integrally with the main body 181, for example,during injection molding.

The main body 181 has an electrode tab drawing hole 187 formed on oneside, through which an electrode tab can be drawn out, and anelectrolyte injection hole 188 formed on the other side, through whichan electrolyte can flow into the electrode assembly 12. Alternatively,the electrolyte injection hole 188 may be omitted. The main body 181 hasa groove 189 with a predetermined width formed on one of its long sides,through which another electrode tab can be drawn out.

Referring to FIG. 3 a and FIG. 3 b, an insulation case 179 for a lithiumrechargeable battery according to an exemplary embodiment of the presentinvention has a gas evacuation hole 190 b formed on a long side of themain body 181 in the shape of a lozenge.

Referring to FIG. 4 a and FIG. 4 b, an insulation case 179 for a lithiumrechargeable battery according to an exemplary embodiment of the presentinvention has a gas evacuation hole 190 c formed on a central portion ofthe main body 181 in the shape of a semi-circle.

Referring to FIG. 5 a and FIG. 5 b, an insulation case 179 for a lithiumrechargeable battery according to an exemplary embodiment of the presentinvention has gas evacuation holes 190 d and 190 e formed on both shortsides of the main body 181 in the shape of a circle and an ellipse,respectively.

As shown in FIG. 2 a, FIG. 3 a, FIG. 4 a, and FIG. 5 a, the gasevacuation holes formed on the insulation case may have various shapesand positions. Additional combinations of size, shape, number, andpositioning of the holes are possible.

FIG. 6 is a sectional view showing a lithium rechargeable batteryaccording to an exemplary embodiment of the present invention.

Referring to FIG. 6, the lithium rechargeable battery includes a can210, an electrode assembly 212 contained in the can 210, and a capassembly 220 coupled to the top of the can 210.

The can 210 has an approximately square shape with an open top and ismade of a metallic material, which may be, but is not limited to,aluminum, aluminum alloy, or stainless steel. The can 210 itself may actas a terminal.

The electrode assembly 212 includes a first electrode 213, a secondelectrode 215, and a separator 214. The first electrode 213 and secondelectrode 215 may be laminated to each other with the separator 214interposed between them and wound in a jelly-roll shape. The first andsecond electrodes 213 and 215 have first and second electrode tabs 216and 217 attached to them, respectively. The first and second electrodetabs 216 and 217 extend upward.

The first and second electrodes 213 and 215 have opposite polarities.Either may act as a positive or negative electrode. Each of the firstand second electrodes 213 and 215 include a collector and either apositive or negative electrode active material applied to at least onesurface of the collector.

The positive electrode collector may be made of stainless steel, nickel,aluminum, titanium, or an alloy thereof or may be made of aluminum orstainless steel that has been surface-treated with carbon, nickel,titanium, or silver. An exemplary embodiment uses aluminum or analuminum alloy. The negative electrode collector may be made ofstainless steel, nickel, copper, titanium, or an alloy thereof or may bemade of copper or stainless steel that has been surface-treated withcarbon, nickel, titanium, or silver. An exemplary embodiment uses copperor a copper alloy.

The positive electrode active material may be lithium-containingtransition metal oxide or a lithium chalcogenide compound. Examples oflithium-containing transition metal oxides include LiCoO₂, LiNiO₂,LiMnO₂, LiMn₂O₄, or LiNi_(1-x-y)Co_(x)M_(y)O₂ where 0≦x≦1, 0≦y≦1,0≦x+y≦1, and M is a metal such as Al, Sr, Mg, or La. The negativeelectrode active material may be crystalline or amorphous carbon, carboncomposite such as thermally decomposed carbon, coke, or graphite, burnedorganic polymer compound, carbon fiber, tin oxide compound, lithiummetal, or lithium alloy.

The separator 214 prevents a short circuit between the first and secondelectrodes 213 and 215 and provides lithium ions with a passage formovement. The separator 214 may be a film made of high-molecularpolyolefin, such as polypropylene or polyethylene. The film may be amultiple film, a micro-porous film, a woven fabric, or a non-wovenfabric.

The cap assembly 220, which is coupled to the top of the can 210,includes a cap plate 240, an insulation plate 250, a terminal plate 260,and an electrode terminal 230. The cap plate 240 is made of a metalplate and corresponds in size to the opening of the can 210. The capplate 240 has a terminal through-hole 241 of a predetermined size formedat its center, an electrolyte injection hole 242 formed one side, and asafety vent 244 formed on the other side. The safety vent 244 may beplaced anywhere so long as it does not interfere with the terminalthrough-hole 241 and the electrolyte injection hole 242. The safety vent244 may, for example, be formed on the can 210 instead of the cap plate240. In this exemplary embodiment, the safety vent 244 is integrallyformed by reducing the sectional thickness of the cap plate 240. Theelectrolyte injection hole 242 is sealed by a plug 243.

The electrode terminal 230 is inserted into the terminal through-hole241 and a tubular gasket 246 insulates the electrode terminal 230 fromthe cap plate 240. The insulation plate 250 is positioned on the lowersurface of the cap plate 240. The terminal plate 260 is positioned onthe lower surface of the insulation plate 250. The bottom of theelectrode terminal 230 is electrically connected to the terminal plate260 with the insulation plate 250 interposed between them.

Either the first electrode tab 216 or the second electrode tab 217 maybe welded to the lower surface of the cap plate 240 and the other tabmay be welded to the terminal plate 260. In this exemplary embodiment,for example, the first electrode tab 216 is welded to the lower surfaceof the cap plate 240 and the second electrode tab is welded to theterminal plate 260.

The electrode assembly 212 has an insulation case 270 positioned on itstop to insulate the electrode assembly 212 from the cap assembly 220 andto fix the position of the electrode assembly 212 and the first andsecond electrode tabs 216 and 217. The insulation case 270 has anelectrode tab drawing hole 273 and also has a gas evacuation hole 272formed below the safety vent 244 on the cap plate 240. Gas generated bythe electrode assembly 212 is easily evacuated via the gas evacuationhole 272 on the insulation case 270. This improves the stability of thebattery and prevents the electrode assembly 212 from swelling.

The insulation case 270 is may be made of an insulating high-molecularresin, such as polypropylene (PP), polyphenylene sulfide (PPS),polyethersulfone (PES), or modified polyphenylene oxide (PPO). PPS hasexcellent heat resistance, dimensional stability, chemical-resistance,low absorptiveness, and is non-flammable. The electrical properties ofPPS vary little as the temperature changes. PES is an amorphous aromaticplastic resin that is resistant to temperatures of up to 200° C. It alsohas excellent dimensional stability, water resistance, transparency, ahigh glass transition temperature of 223° C., a low degree of expansionof 2.3×10⁻⁵/° C., and good mechanical strength. Modified PPO is anon-flammable resin with excellent mechanical properties and heatresistance. Its physical properties undergo little degradation at lowtemperatures and contracts very little during shaping.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A lithium rechargeable battery, comprising: an electrode assemblythat includes first and second electrodes wound together with aseparator interposed between them; a cap assembly comprising a cap plateand an insulation plate; an insulation case positioned on top of theelectrode assembly and spaced apart from the cap assembly between theelectrode assembly and the cap assembly; and a can containing theelectrode assembly and the insulation case, wherein the cap plate iscoupled to the top of the can, wherein a safety vent is formed on thecap plate or the can, wherein the insulation case has at least one of anelectrolyte injection hole and an electrode tab drawing hole, whereinthe insulation case has at least one other hole, and wherein the otherhole is a gas evacuation hole and is positioned directly below thesafety vent, wherein the insulation case has at least one supporterformed on its side and at least one portion on its side where thesupporter is not formed.
 2. The lithium rechargeable battery of claim 1,wherein the other hole has a shape selected from the group of a circle,an ellipse, a semi-circle, a square, a triangle, and a lozenge.
 3. Thelithium rechargeable battery of claim 1, wherein the other hole isformed on a long side of the insulation case.
 4. The lithiumrechargeable battery of claim 1, wherein the other hole is formed on acentral portion of the insulation case.
 5. The lithium rechargeablebattery of claim 1, wherein the other hole is formed on a short side ofthe insulation case.
 6. The lithium rechargeable battery of claim 1,wherein the other hole contacts an edge of the insulation case.
 7. Thelithium rechargeable battery of claim 1, wherein the insulation case ismade of a high-molecular resin.
 8. The lithium rechargeable battery ofclaim 7, wherein the molecular resin is one of polypropylene,polyphenylene sulfide, polyethersulfone, and modified polyethersulfone.9. The lithium rechargeable battery of claim 1, wherein the at least onesupporter extends upward.
 10. The lithium rechargeable battery asclaimed in claim 1, wherein the at least one supporter is integral withthe insulation case.
 11. The lithium rechargeable battery of claim 1,wherein the insulation case has one supporter formed on each of its foursides.
 12. The lithium rechargeable battery of claim 1, wherein theinsulation case has a plurality of other holes.